1. Field of the Invention
This invention relates to novel perfluoropolyether and a process for producing the same, and particularly to novel perfluoropolyether obtained by reaction of tetrafluoroethylene with oxygen in a fluorinated solvent or chlorofluorinated solvent under ultraviolet irradiation and a process for producing the same.
2. Description of the Prior Art
It is well-known to produce perfluoropolyether by reaction of tetrafluoroethylene with oxygen in a fluorinated solvent or chlorofluorinated solvent under ultraviolet irradiation (see, for example, Japanese Patent Publication No. 55-50052, etc.).
The thus obtained perfluoropolyether has active fluorine and active oxygen bonds and a broad range of controllable viscosity, and thus is useful as an intermediate for synthesis of a cross-linking agent, a polymeric surfactant, etc.
Neutral perfluoropolyethers whose active groups are decreased by heat treatment, fluorine treatment, etc. of the said perfluoropolyether has a wide range of industrial applications as base oil for high performance grease, vacuum pump oil, a special lubricant for magnetic disks, a lubricant for rockets, etc. owing to higher chemical and physical stabilities orignating from its structure.
In these applications, the molecular weight of perfluoropolyether is an important problem. The said Japanese Patent Publication No. 55-50052 discloses that the molecular weight depends upon the dosage of ultraviolet irradiation and the feed rate of the monomer for the reaction, and that the molecular weight is lowered with increasing dosage of ultraviolet irradiation and increased with increasing feed rate of the monomer.
This relationship means that, in order to obtain a product of, for example, lower molecular weight, an ultraviolet irradiation apparatus of larger capacity must be used, when viewed from the apparatus design, whereas, in order to lower the feed rate, very disadvantageous conditions must be selected, when viewed from the production cost and reaction efficiency.
As a result of extensive studies of a process for producing perfluoropolyether having a low molecular weight, free from these problems, the present inventors have found that these problems can be effectively solved and perfluoropolyether having a desired range of molecular weight can be obtained according to a telomerization procedure using a halogenated hydrocarbon chain transfer agent as a telogen, and have found at the same time that the thus obtained perfluoropolyether has an active halogen bond originating from the employed halogenated hydrocarbon chain transfer agent in the molecule, and thus can be used as a novel intermediate.